Process for preventing development defect and composition for use in the same

ABSTRACT

The composition for preventing development-defects containing (1) an ammonium salt, a tetraalkylammonium salt or a C 1  to C 4  alkanolamine salt of C 4  to C 15  perfluoroalkylcarboxylic acid, C 4  to C 10  perfluoroalkylsulfonic acid and perfluoroadipic acid, or (2) a fluorinated alkyl quaternary ammonium salt of inorganic acid, wherein said surfactant is formed at the equivalent ratio of acid to base of 1:1-1:3 is applied on a chemically amplified photoresist coating on a substrate having a diameter of 8 inches or more. The chemically amplified photoresist coating is baked before and/or after applying the composition for preventing development-defects described above. Then, the baked coating with the development-defect preventing composition coating is exposed to light, post-exposure-baked, and developed. By this process, compared with the case of not using the composition for preventing development-defects, the amount of reduction in film thickness of the photoresist subsequent to development treatment is made further bigger by 100 Å to 600 Å, and the development-defects on a substrate having a diameter of 8 inches or more is reduced as well as a resist pattern having a good cross section form can be formed without T-top form etc.

This application is a United States National Stage Patent Applicationunder 35 U.S.C. §371 of International Patent Application No.PCT/JP03/07354, filed Jun. 10, 2003, which claims priority to JapanesePatent Application No. 2002-181127, filed Jun. 21, 2002, the contents ofboth documents being incorporated herein by reference.

TECHNICAL FIELD

This invention relates to a process for forming a resist pattern with agood profile by using a positive-working chemically amplifiedphotoresist, and to a composition for preventing development-defectsused in this process. More particularly, it relates to a process forforming a resist pattern by which a resist pattern with a good profilecan be formed all over the large-diameter substrate when a resistpattern is formed by pattern-wise exposing a large-diameter substratehaving formed thereon a chemically amplified photoresist coatingfollowed by development, and to a composition for preventingdevelopment-defects used in this process.

BACKGROUND ART

In manufacturing semiconductor elements, lithographic technology hasbeen employed in which a photoresist coating is formed on a substratesuch as a silicon wafer and, after selectively irradiating the coatingwith actinic rays, development treatment is conducted to form a resistpattern on the substrate thereby.

In recent years, in order to attain higher degree of integration in LSI,patterning technology for forming patterns with a finer line width in alithographic process has been making a rapid progress. For forming apattern with a finer line width, various proposals have been made withrespect to all steps of the lithography and all materials to be usedtherein including photoresists, antireflective coatings, exposingmethods, exposing apparatus, developing agents, developing processes anddeveloping apparatus. For example, Japanese Patent Publication No.2,643,056 and Japanese Unexamined Patent Publication No. H7-181685describe that an antireflective surface coating containing afluorine-containing compound with a low refractive index is formed on aresist coating to prevent detrimental influences of reflected light fromthe resist surface on formation of a resist pattern thereby. When anantireflective coating is coated on a resist layer, degree of vibrationamplitude of the thickness of a resist coating v.s. sensitivity curvebecomes smaller. Therefore fluctuation in sensitivity of resist becomessmaller even when thickness of the resist layer fluctuates, which leadsthe advantage of a decreased fluctuation in dimension of resist patternsformed. In addition, the antireflective surface coating serves todecrease standing wave to be caused by interference between incidentlight and reflected light or between one reflected light and anotherreflected light. Recently, technology of forming a resist pattern havinga desired line width without providing the antireflective surfacecoating has also been developed. As examples thereof, there areillustrated that an underlying substrate is made plane to depressfluctuation in dimension due to fluctuation in thickness of the resistlayer as described above, or a mask pattern is finely adjusted inadvance according to fluctuation in dimension of the resist.

With regard to exposing apparatus, there has been proposed a process ofusing a light source emitting radiation of a short wavelength, which isadvantageous for formation of a superfiner pattern, such as deep UV raysof KrF excimer laser (248 nm) or ArF excimer laser (193 nm) or, further,X rays or electron beams, and some of them have been coming intopractice.

On the other hand, improvement in the yield of semiconductor integratedcircuits has been paid attention as an extremely important matter inmanufacturing them. There exist many factors by which the yield ofsemiconductor integrated circuits is decided. One of the factors ispatterning failure upon forming a pattern using a resist. Thispatterning failure of a resist pattern is caused, for example, by thedust existing in the resist or sticking onto the surface of the resistlayer, by the deterioration of the resist due to floating chemicalspecies in the clean room, by the coating failure of the resist or thelike, or by the development failure. As an example of deterioration dueto chemical species floating in a clean room, there is given a processusing a chemically amplified photoresist. In this process, thechemically amplified photoresist is susceptible to influence of acidicsubstances, basic substances and moisture in the atmosphere. Therefore,when the period between pattern-wise exposure and PEB (post exposurebake) is prolonged (post exposure delay) or due to intermixing with aresist, there results a change in dimension of a pattern, for example,by formation of a T-topped resist pattern in the case where apositive-working photoresist is used as resist, or formation of around-topped resist pattern in the case where a negative-workingphotoresist is used as resist.

In addition, defects upon developing a resist layer have become aproblem. As examples of defects upon development, there are givenformation of scum in line-and-space type resists and hole-openingfailure in contact hole type resists. Several causes may be consideredfor the hole-opening failure of contact holes, but the most popularhole-opening failure is one caused by residues after development. As acause of these defects, there is illustrated insufficient dissolution ofexposed portions into a developing solution due to insufficient contactbetween the developing solution containing water as a major componentand the surface of a resist coating upon bringing the developingsolution into contact with the resist surface, which leads tohole-opening failure of portions which are designed to open essentially.It is also thought that hardly-solubles in the developing solution mightre-deposit onto the surface of the resist upon rinsing with water afterdevelopment.

Further, it is necessary to enhance contrast of a resist in order toform a finer pattern. In general, in order to improve contrast of acontact hole type resist, a technique of increasing a protecting ratioof hydrophilic groups in a major component polymer is used with respectto, for example, positive-working chemically amplified photoresists.However, when the protecting ratio is increased, the resist surface isliable to become hydrophobic, leading to deterioration in wettingproperties for the developing solution.

Various investigations have been conducted to solve the above-describedproblems. For example, Japanese Unexamined Patent Publication No.H9-246166 proposes to treat the surface of a photoresist with plasma torender the surface hydrophilic thereby, thus improving wettingproperties of the resist for a developing solution and decreasingdevelopment defects. This technique, however, requires introduction ofan additional apparatus for the plasma treatment as well as includes theproblem of decrease in throughput.

In addition, various attempts for decreasing the development defects byoptimizing development sequence have been made as well. For example,Japanese Examined Patent Publication No. H4-51020 describes to improvewetting properties of a positive-working resist for a developingsolution by adding an acetylenealcohol type surfactant to the developingsolution, thereby forming a pattern having no development defects.Although some effects can be obtained by this technique, the effects areat present still insufficient in ultra-fine working using the aforesaidchemically amplified photoresists. In addition, Japanese UnexaminedPatent Publication No. S61-179435 describes a method of optionalformation of surface coating, which is effective for improving wettingproperties for a developing solution, as well as a method of adding asurfactant to the developing solution and a method of plasma-treatingthe surface of a resist coating, for preventing development defectsresulting from lack of wetting properties for the developing solution.

Particularly in the case where surface coating for decreasing thedevelopment defects is formed on a chemically amplified photoresist,there may cause a round-topped or a T-topped pattern which may cause atrouble in an etching process when a surface coating composition, whichis coated to reduce this development-defect, is compatible with achemically amplified resist. For example, in the patent publication ofJP 2643056, as an anti-reflective coating composition to form ananti-reflective coating on a photoresist film, a composition comprisinga water-soluble polymer binder and a water-soluble fluorocarbon compound(for example, a quaternary ammonium salt of perfluorocarboxylic acid orperfluorosulfonic acid, and so on) was disclosed. However, in saidpublication, there is no description of a control on the amount ofreduced thickness in film thickness after developing a chemicallyamplified photoresist. In addition, the method described in thepublication has a problem. That is, in the case where theanti-reflective coating composition described in said publication isused, when the chemically amplified photoresist is a positive-workingphotoresist, a pattern profile of a resist pattern formed is likely tobecome a T-letter-shape (T-top), and when being a negative-workingphotoresist, the pattern profile of the resist pattern formed is likelyto become a round shape (round-top), thereby a problem of patterndimension deterioration being taken place.

Further, it is said that problems in attaining uniform thickness ofcoating and uniform development to be caused with a recent increase indiameter of a substrate such as a silicon wafer make it difficult toform a finer pattern. For example, a paddle developing method has so farbeen popularly employed for developing a resist coating on the siliconwafer. In the paddle developing method, a developing solution is droppedonto a resist coating formed on a substrate, and the substrate is spunto form a thin film of the developing solution all over the resistcoating, thus development of the resist coating being conducted.However, there generates a difference in circumferential speed betweenthe central portion and the peripheral portion of the substrate, therebya difference in speed of the coating generating. Thus, developingconditions become different between the central portion of the wafer andthe peripheral portion thereof. In this situation, particularly when achemically amplified photoresist is used as a resist and a developingprocess of a large-diameter substrate having a diameter of 8 inches ormore is conducted, development defects in the peripheral portion arecaused in some cases which have not conventionally been observed intreating a resist coating formed on a substrate having a diameter of 6inches or less.

Therefore, in order to improve a yield in manufacturing semiconductorintegrated circuits and so on, a process for forming a resist patternhas been desired which enables one to reduce development defects to becaused upon development including a development defect of a chemicallyamplified photoresist in the periphery of a larger diameter substratesuch as a silicon wafer caused by increasing in diameter of a substrate,and which does not cause pattern failure such as T-top or round topafter development for coping with formation of finer patterns earnestlyfor forming a finer resist pattern.

As a method to reduce such development defects, Japanese UnexaminedPatent Publication No. 2002-6514 describes that by applying acomposition for reducing a development-defect containing afluorine-containing surfactant on a chemically amplified photoresistcoating, the amount of reduced thickness in film thickness of thechemically amplified photoresist after exposure to light and developmentis made bigger by further 10 Å to 500 Å compared with the case withoutapplying this composition for reducing development-defects to form apattern without development-defect thereby. In this publication, as asurfactant which is contained in a composition for reducingdevelopment-defects of a positive-working chemical amplifiedphotoresist, it is disclosed to use a surfactant which is formed withexcess of acid for the composition ratio of organic acid and base and inwhich at least acid remains. However, it is difficult to make this filmthickness reduction large by using the composition for reducingdevelopment-defects. When elimination of T-top can be realized in thecase where film thickness reduction would be made large, there is alimit to form a pattern with good profiles by using the composition forreducing development-defects. In addition, in the publication, there isno description that a film thickness reduction can be controlledquantitatively. Because of this there is a problem that it is difficultto obtain the composition for reducing development-defects which canprovide an optimal film thickness reduction in order to make thepattern-profiler rectangular and good.

In consideration of the above-described situation, an object of thepresent invention is to provide a process of forming a resist pattern byusing a composition for preventing development defects by whichdevelopment defects of a positive-working chemically amplifiedphotoresist is particularly reduced upon developing of a large diametersubstrate having a diameter of 8 inches or more and deterioration ofpattern profiles does not be caused such as T-top or round top which areinconvenient for an etching step due to detrimental influences of aprocessing atmosphere and intermixing between the surface coating andthe resist, wherein an occurrence of development defects on a substratewith large diameter and a pattern profile after development can beimproved with optimal film thickness reduction by use of a compositionfor preventing development defects which can make a film thicknessreduction after development bigger compared with the process so farknown as well as control the amount of film thickness reduction, andcoping with optimal film thickness reduction is easy.

Another object of the present invention is to provide a composition forpreventing development-defects used in above-described process.

As a result of intensive investigations, the inventors have found thatin a process of forming a resist pattern in which a composition forpreventing development-defects containing a particularfluorine-containing surfactant is applied on a positive-workingchemically amplified photoresist to render the surface thereofhydrophilic, then pattern-wise exposed to light and developed, theamount of film thickness reduction subsequent to a development of apositive-working chemically amplified photoresist can be enlarged whenthe equivalent of acid and base which constitute the surfactant is madeexcess of base compared with acid upon a formation of a surfactant whichis contained in the composition for preventing development defects, andthe amount of film thickness reduction of a photoresist subsequent to adevelopment can be increased or decreased by controlling the amount ofthe base used at this time, thus being achieved the present invention.

DISCLOSURE OF THE INVENTION

The present invention provides a process for forming a resist pattern,which increases the amount of reduction in thickness of a chemicallyamplified photoresist coating after development by 100 Å to 600 Å incomparison with the case of not applying the composition for preventingdevelopment-defects, comprising: a step of forming a chemicallyamplified photoresist coating on a substrate having a diameter of 8inches or more by application; a step of applying a composition forpreventing development-defects containing a surfactant on the chemicallyamplified photoresist coating; a step of baking after at least eitherthe step of forming the chemically amplified photoresist coating byapplication or the step of applying the composition for preventingdevelopment-defects; a step of selectively exposing the chemicallyamplified photoresist coating; a step of post-exposure baking thechemically amplified photoresist coating; and a step of developing thechemically amplified photoresist coating,

wherein said surfactant is at least one member selected from the groupconsisting of (1) an ammonium salt, a tetraalkylammonium salt or a C₁ toC₄ alkanolamine salt of C₄ to C₁₅ perfluoroalkylcarboxylic acid, (2) anammonium salt, a tetraalkylammonium salt or a C₁ to C₄ alkanolamine saltof C₄ to C₁₀ perfluoroalkylsulfonic acid, (3) a quaternary ammonium saltof perfluoroadipic acid, and (4) a fluorinated alkyl quaternary ammoniumsalt of inorganic acid which is at least one member selected from thegroup consisting of sulfric acid, hydrochrolic acid, nitric acid andhydroiodic acid, at the same time said surfactant being one that isformed at the equivalent ratio of an acid to a base of 1:1-1:3.

The present invention also provides a composition for preventingdevelopment-defects which contains a surfactant and is used for theprocess of forming a resist pattern that increases the amount ofreduction in thickness of a chemically amplified photoresist coatingafter development by 100 Å to 600 Å in comparison with the case of notapplying the composition for preventing development-defects, comprising:a step of forming a chemically amplified photoresist coating on asubstrate having a diameter of 8 inches or more by application; a stepof applying a composition for preventing development-defects containinga surfactant on the chemically amplified photoresist coating; a step ofbaking after at least either the step of forming the chemicallyamplified photoresist coating by application or the step of applying thecomposition for preventing development-defects; a step of selectivelyexposing the chemically amplified photoresist coating; a step ofpost-exposure baking the chemically amplified photoresist coating; and astep of developing the chemically amplified photoresist coating,

wherein said surfactant is at least one member selected from the groupconsisting of (1) an ammonium salt, a tetraalkylammonium salt or a C₁ toC₄ alkanolamine salt of C₄ to C₁₅ perfluoroalkylcarboxylic acid, (2) anammonium salt, a tetraalkylammonium salt or a C₁ to C₄ alkanolamine saltof C₄ to C₁₀ perfluoroalkylsulfonic acid, (3) a quaternary ammonium saltof perfluoroadipic acid, and (4) a fluorinated alkyl quaternary ammoniumsalt of inorganic acid which is at least one member selected from thegroup consisting of sulfric acid, hydrochrolic acid, nitric acid andhydroiodic acid, at the same time said surfactant being one that isformed at the equivalent ratio of acid to base of 1:1-1:3.

CONCRETE MODE OF THE INVENTION

The present invention is described in more detail below. In a resistpattern forming process of the present invention, the amount ofreduction in thickness of the chemically amplified photoresist coatingafter development is made bigger by 100 Å to 600 Å in comparison withthe case of not applying the composition for preventingdevelopment-defects on the chemically amplified photoresist coating. Inorder to make the amount of reduction in thickness of photoresist filmafter developing treatment big in amount, when forming the surfactantdescribed in above items (1) to (4) which is contained in thecomposition for preventing development-defects, an equivalent quantityof base is made excessive to that of acid in the present invention.

As an organic acid which is used upon forming surfactants (1) to (3)described above which are contained in the composition for preventingdevelopment-defects, there are exemplified preferably functionalfluorocarbon compounds, particularly perfluoroalkylcarboxylic acid suchas C₄ to C₁₅ perfluoroalkylcarboxylic acid, perfluoroalkylsulfonic acidsuch as C₄ to C₁₀ perfluoroalkylsulfonic acid, and perfluoroadipic acid.As a base, there are exemplified ammonia, amines and quaternary ammoniumalkyl hydroxide and ammonia, tetramethylammonium hydroxide and C₁ to C₄alkanolamine are particularly preferred. The organic acid and the basesuch as amine, quaternary ammonium alkyl hydroxide or ammonia are mixedin an aqueous solution, and for example, an ammonium salt, atetraalkylammonium salt such as a tetramethylammonium salt or an aminesalt such as C₁ to C₄ alkanol amine salt, of an organic acid is formed.When forming an above-described surfactant (4), an inorganic acid suchas sulfuric acid, hydrochloric acid, nitric acid, hydroiodic acid, andthe like is used as the acid, and on the other side, fluorinated alkylquaternary ammonium hydroxide etc. is used as the base.

In the present invention, these surfactants are formed by solving thedetermined amount of the acid and the base in water. At this time, theamount of the formed surfactant in the aqueous solution is made 0.1 to25 weight-%, more preferably 2 to 4 weight-%. The aqueous solution isused as a composition for reducing development defects. If necessary,additives are further solved in this aqueous solution and the resultingsolution may be used as a composition for preventingdevelopment-defects. In addition, the surfactant-containing aqueoussolution may be formed by adjusting the concentration, for example, byadding the preformed high concentration aqueous surfactant to watercontaining additives if necessary or vise versa by diluting thepreformed high concentration aqueous surfactant with anadditive-containing aqueous solution if necessary.

In this situation, the amount of reduction in thickness of the resistlayer can be optimized by properly adjusting the mixing ratio of theabove-described acid and base such as an amine, a quaternary ammoniumhydroxide, and ammonia to adjust basicity of the composition inconsideration of the kind of a chemically amplified photoresist to beused or processing conditions. It means that, upon forming a surfactant,a mixing amount of the acid and the base is controlled as that theequivalent of a base is excessive to the equivalent of an acid in thepresent invention. At this time, the amount of reduction in filmthickness after development of photoresist is increased by increasingthe amount of base to be used. Accordingly the amount of reduction infilm thickness upon developing resist can be controlled to obtain anoptimized result by properly adjusting the mixing ratio of the acid tothe base such as an amine, a quaternary ammonium hydroxide, and ammoniain accordance with the kind of a chemically amplified photoresist to beused or processing conditions. In the composition for preventingdevelopment-defects to be applied for positive-working chemicallyamplified photoresist, the ratio of acid to base, for example amine, isusually 1:1 to 1:3, preferably 1:1 to 1:2 in equivalent ratio.

In the composition for preventing development defects of the presentinvention, a water-soluble resin and a various kinds of additives can beformulated within the limit wherein its performance is not damaged, ifnecessary.

As a water-soluble resin which is used for the composition forpreventing development defects of the present invention, there can beillustrated, for examples, poly(vinyl alcohol), poly(acrylic acid),poly(vinylpyrrolidone), poly(α-trifuluoromethyl acrylic acid),poly(vinyl methyl ether-co-maleic anhydride), poly(ethyleneglycol-co-propylene glycol), poly(N-vinylpyrrolidone-co-vinyl acetate),poly(N-vinylpyrrolidone-co-vinyl alcohol),poly(N-vinylpyrrolidone-co-acrylic acid),poly(N-vinylpyrrolidone-co-methyl acrylate),poly(N-vinylpyrrolidone-co-methacrylic acid),poly(N-vinylpyrrolidone-co-methyl methacrylate),poly(N-vinylpyrrolidone-co-maleic acid),poly(N-vinylpyrrolidone-co-dimethyl maleate),poly(N-vinylpyrrolidone-co-maleic anhydride),poly-(N-vinylpyrrolidone-co-itaconic acid),poly(N-vinylpyrrolidone-co-methyl itaconate),poly(N-vinylpyrrolidone-co-itaconic anhydride), fluorinated polyether,etc. Above all, poly(acrylic acid), poly(vinylpyrrolidone), andfluorinated polyether are especially preferred.

As the additives to be used in the composition for preventingdevelopment-defects of the present invention, there can be illustrated,for example, surfactants to be added for improving coating properties,such as nonionic surfactants, anionic surfactants and amphotericsurfactants. As the nonionic surfactants, there are exemplifiedpolyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether,polyoxyethylene oleyl ether and polyoxyethylene cetyl ether,polyoxyethylene fatty acid diesters, polyoxyfatty acid monoester,polyoxyethylene-polyoxypropylene block polymer, and acetylene glycolderivatives. As the anionic surfactants, there are exemplified ammoniumsalts or organic amine salts of alkyldiphenyl ether disulfonic acid,ammonium salts or organic amine salts of alkyldiphenyl ether sulfonicacid, ammonium salts or organic amine salts of alkylbenzenesulfonicacid, ammonium salts or organic amine salts of polyoxyethylene alkylether sulfuric acid, and ammonium salts or organic amine salts of alkylsulfuric acid. As the amphoteric surfactants, there are exemplified2-alkyl-N-carboxymethyl-N-hydroxyethyl-imidazolinium betaine andlaurylamidopropyl hydroxysulfone betaine.

Further, as water to be used in the composition for preventingdevelopment-defects of the present invention, water from which organicimpurities, metal ions, etc. have been removed by distillation, anion-exchange treatment, a treatment through filter or various adsorptiontreatments are preferably illustrated.

Additionally, in order to improve coating properties, a water-solubleorganic solvent can be used together with water. The water-solubleorganic solvent is not particularly limited as long as it can be solublein water in a concentration of 0.1 wt % or more. Examples of the organicsolvent include alcohols such as methyl alcohol, ethyl alcohol andisopropyl alcohol, ketones such as acetone and methyl ethyl ketone,esters such as methyl acetate and ethyl acetate, and polar solvents suchas dimethylformamide, dimethylsulfoxide, methyl cellosolve, cellosolve,butyl cellosolve, cellosolve acetate, butylcarbitol and carbitolacetate. These specific examples are merely illustrated as examples ofthe organic solvents, and the organic solvents to be used in the presentinvention are not limited only to these solvents.

In addition, optimization of the amount of reduction in thickness of theresist coating in the present invention may also be attained by properlyadjusting baking time or baking temperature of the resist and thecomposition for preventing development-defects as well as optimizationby the composition itself for reducing development defects. As to theprebaking temperature for the resist, there are generally two types inaccordance with photoresist compositions to be used. That is, one typerequires a high energy and generally requires to bake at a temperatureof about 100° C. to about 150° C., and another type does not require somuch energy in comparison with the former and requires to bake at atemperature of 100° C. or lower. In addition, prebaking temperature forthe composition for preventing development-defects is generally 60° C.to 100° C. which is high enough to remove the solvent. Further,post-exposure baking of the resist is generally about 100° C. to about150° C. For example, in the case where T-tops are formed afterdevelopment, formation of such T-tops can be avoided in some cases bysuch combination of baking temperatures for the resist and thecomposition for preventing development-defects that resist-prebakingtemperature is set at a lower level while prebaking temperature for thecomposition for preventing development-defects at a level of 100° C. orhigher. In addition, too much reduction in thickness of the resistcoating disadvantageous in an etching step can be avoided by optionallydelaminating or dissolving away the composition for preventingdevelopment-defects after exposure.

Thickness of the coating of the composition for preventingdevelopment-defects in the present invention may be such that itprovides enough chemical action to more reduce thickness of the resistcoating in comparison with the case of not applying the composition forpreventing development-defects. The thickness of the coating ispreferably 80 Å to 10,000 Å, more preferably 330 Å to 990 Å. Coating ofthe composition for preventing development-defects can be conducted byany of known coating methods such as a spin coating method.

The chemically amplified photoresist to be used as a resist in thepresent invention may be any of known positive-working chemicallyamplified photoresists. As the positive-working chemically amplifiedphotoresist, there are known a number of ones including that which iscomposed of a combination of a polymer wherein polyhydroxystyrene isprotected with t-butoxycarbonyl group and a photo acid generator (see,H. Ito and C. G. Willson: Polym. Eng. Sci., 23, 1012 (1983)). Thicknessof the coating may be such that a resist pattern obtained afterdevelopment can suitably exert its performance during etching in theetching step, and is generally about 0.3 to 1.0 μm.

The pattern-forming method of the present invention can favorably beapplied upon formation of a pattern on a substrate having a diameter of8 inches or more. As the substrate, a silicon substrate is common, andof course may be those wherein a metal layer or an oxide or nitridelayer such as silicon oxide, silicon nitride or silicon oxide nitride isformed on silicon. In addition, the substrate itself is not limited tosilicon but may be any of substrate materials having so far been usedfor manufacturing IC such as LSI.

As to the method for coating the chemically amplified photoresist andbaking of the chemically amplified photoresist layer and the layer ofreducing development defect compositions, exposing method, developingagents, and developing methods, any ones or any conditions having so farbeen employed for forming a resist pattern using a chemically amplifiedphotoresist may be employed. Further, as an exposing light source to beused in the exposing step, any of UV rays, deep UV rays, X rays andelectron beams may be used.

BEST MODE FOR PRACTICING THE INVENTION

The present invention will now be described more specifically byreference to Examples which, however, are not to be construed to limitthe present invention in any way.

EXAMPLE-1

1.3 parts by weight of polyacrylic acid having weight average molecularweight of 3,000 as determined by polystyrene standards as awater-soluble polymer, 2.0 parts by weight of perfluoro-octylic acid(C₇F₁₅COOH) as an organic acid, 0.46 parts by weight oftetramethylammonium hydroxide (TMAH) (equivalent ratio (mole) of organicacid and base is 1:1.04) as a base were mixed up. Pure water was addedthereto to make the total amount 100 parts by weight. Then, the solutionwas solved homogeneously at room temperature, and filtered with a 0.1μm-filter to obtain the composition for preventing development-defects.

On the other hand, a positive-working photoresist comprising acetal typepolymer manufactured by Clariant (Japan) K.K. (AZ DX3301P, ‘AZ’ is aregistered trade mark.) was applied on an 8 inches silicon wafer by aspin coater made by Tokyo Electron Co. (Mark 8). It was pre-baked on ahot plate at 90° C. for 90 seconds to form a photoresist film of 480 nmin thickness on a silicon wafer. The film thickness was measured by filmthickness measuring equipment SM300 manufactured by Prometric Co.

Subsequently the above described composition for preventingdevelopment-defects was applied on the photoresist film by using thesame spin coater as the above. It was then pre-baked on a hot plate at90° C. for 60 seconds to form a film for preventing development-defectson a photoresist film of 450 Å in thickness. Next, exposure to light wasconducted by using KrF reduced projection exposure equipment, FPA3000-EX5, PEB was conducted on a hot plate at 110° C. for 60 seconds.Using alkali developer, AZ 300MIF Developer (2.38 weight %tetramethylammonium hydroxide aqueous solution; ‘AZ’ is a registeredtrademark.) as a developer, it was paddle-developed on the condition of23° C. for 1 minute, to obtain a resist pattern having 1:1 line andspace width. And also the film thickness after development was measuredusing the same equipment as one described above. The amount of filmreduction in thickness was obtained by deducting the film thicknessafter development from one before development. The cross sectional formof the formed resist pattern was observed by Scanning ElectronicMicroscope (SEM). Observation result of the cross-sectional form of theresist pattern and the amount of film reduction in thickness are shownin the Table-1 described below.

EXAMPLES 2 to 5

The same manner was taken as in Example-1 except that the equivalent(mole) ratios of base were made as described in Table-1 below and theresults in Table-1 were obtained.

TABLE 1 Reduction Film thickness Film thickness amount in before afterfilm Development Development thickness Organic Pattern (Å) (Å) (Å) AcidBase Profile Example-1 4819 4589 230 1 1.04 almost rectangular Example-24789 4460 329 1 1.25 rectangular Example-3 4796 4395 401 1 1.38rectangular Example-4 4837 4379 458 1 1.52 almost rectangular Example-54809 4299 510 1 2.00 almost rectangular

COMPARATIVE EXAMPLE-1

In the same manner as in above described Example-1, the silicon wafer onwhich a positive-working chemically amplified photoresist was appliedwas prepared. Then, exposure to light, PEB and development wereconducted in the same manner as in Example-1 except that the compositionfor preventing development-defects was not applied thereon and a patternform of resist cross section was observed and the amount of reduction infilm thickness was measured. The result is shown in Table-2 describedbelow.

TABLE 2 Film thickness Film thickness Reduction amount before after infilm Development Development thickness Pattern Å Å Å Profile Comparative4801 4698 103 T-top Example-1

COMPARATIVE EXAMPLE-2

Perfluorooctyl acid (C₇F₁₅COOH) was added into the composition used inthe Example-1 described above, mixed up to be excessive by acid having1:0.9 of molar ratio of acid to base. Pure water was added therein,followed by solving at room temperature homogeneously. Next, it wasfiltered through 0.1 μm filter to obtain the composition for preventingdevelopment-defects containing a surfactant having the almost sameconcentration as in Example-1. Treating in the same manner as inExample-1 except for using this composition for preventingdevelopment-defects, the result in Table-3 was obtained.

COMPARATIVE EXAMPLE-3

Treating in the same manner as in Comparative Example-1 except formaking the molar ratio of perfluorooctylic acid and base 1:0.95, theresult in Table-3 was obtained.

TABLE 3 Film Film Reduction thickness thickness amount in before afterfilm Development Development thickness Pattern (Å) (Å) (Å) Acid BaseProfile Com- 4820 4649 171 1 0.90 T-top parative Exam- ple-2 Com- 48054624 181 1 0.95 T-top parative Exam- ple-3

As being obvious from the results described in the above Table-1 andTable-2, it was confirmed that the reduction amount in film thickness islikely to increase as addition of a base and to decrease as addition ofan acid. And then if these ratios of base to be added are made within acertain limit, the resist pattern profile to be formed can be greatlyimproved.

EFFECTS OF INVENTION

As described above in details, by using the composition for preventingdevelopment-defects of the present invention, T-top pattern form of achemically amplified positive-working photoresist can be eliminated, forexample, which is caused by PED or by intermixing with resist, and anexcellent pattern profile can be made having no development-defects evenin the substrate with a large diameter of 8 inches or more.

INDUSTRIAL APPLICABILITY

The process and composition for preventing development-defects of thepresent invention are the good resist pattern-forming method used uponforming a chemically amplified photoresist coating on a substrate with alarge diameter and the composition for preventing development-defectsused for the method.

1. A process for forming a resist pattern, which increases the amount ofreduction in thickness of a chemically amplified positive photoresistcoating after development by 100 Å to 600 Å in comparison with the caseof not applying the composition for preventing development-defects,comprising: a step of forming a chemically amplified positivephotoresist coating on a substrate having a diameter of 8 inches or moreby application; a step of applying a composition for preventingdevelopment-defects containing a surfactant on the chemically amplifiedpositive photoresist coating; a step of baking after at least either thestep of forming the chemically amplified positive photoresist coating byapplication or the step of applying the composition for preventingdevelopment-defects; a step of selectively exposing the chemicallyamplified positive photoresist coating; a step of post-exposure bakingthe chemically amplified positive photoresist coating; and a step ofdeveloping the chemically amplified positive photoresist coating,wherein said surfactant is at least one member selected from the groupconsisting of (1) a tetraalkylammonium salt of C₄ to C₁₅perfluoroalkylcarboxylic acid and (2) a tetraalkylammonium salt of C₄ toC₁₀ perfluoroalkylsulfonic acid, at the same time said surfactant beingone that is formed at the equivalent ratio of acid to base of1:1.04-1:3, and further where the composition for preventingdevelopment-defects has an equivalent excess of base as compared toacid.